These are some basic steps on how to allocate more RAM to your game.
Step 1 - Open the Launcher.
Step 2 - Click the 'installations' button
Step 3 - Choose the profile you want to allocate more RAM to (e.g. Latest Release)
Step 4 - Click the 'more options' button
Step 5 - You will see alot of text, only concentrate on the first line saying -Xmx2G
Step 6 - Replace 2G with how much RAM you want to allocate (e.g. "4G" = 4GB of RAM allocated)
32-bit system only supports up to 4GB RAM memory. Therefore, most 32-bit based systems only support a maximum of 2GB to be allocated to Java. The limit depends on the system, if you got an error, try less allocation.
If you are not using the native Java that comes with the launcher, be sure to use the latest and correct version of Java (64bit on 64bit-OS-Systems is recommended).
How much RAM do I have?
The easiest way to see how much RAM you have on Windows is to open the Task Manager and change to the Performance Tab. Look how much Physical Memory is available. On MacOS, go to the Apple Menu, select About This Mac. This window shows you your total amount of RAM.
Note that other programs and your system also need RAM to work. For example, if you run TeamSpeak or Firefox in background, you should leave enough memory for this software to run.
Some numbers for reference:
Windows 7: 1 GB RAM (32-Bit) or 2 GB RAM (64-Bit)
Windows 8 / 8.1: 1 GB RAM (32-Bit) or 2 GB RAM (64-Bit)
Windows 10: 2 GB RAM
Linux: 1-2 GB
Skype: 256 MB
Teamspeak: 64 MB
It is recommended to never allocate more than half your system RAM to the game. Also be aware that allocating more RAM does not necessarily make the game faster.
Something doesn't work? You got an error?
First of all check for spelling mistakes. Also important: JVM arguments are case-sensitive
Try to install the non-native version of Java (the download can be found here).
If you go that, make sure to set your "Java Executable" in the launcher
to the non-native javaw.exe (e.g. if you installed Java 1.8.0_181, set
it to C:\Program Files\Java\jre1.8.0_181\bin\javaw.exe). Please note that Java 9 and above are not yet fully supported.
Add -Xms1G and try again
Lower the numbers if your issue still persists.
Check if you've enough free RAM, and make sure you use 64-bit when allocating more than 2GB or RAM.
You found a fault in the post? Something is missing? Please let me know on #minecrafthelp on Esper, on the official Minecraft Discord or leave a reply here!
In some cases I have actually seen a large amount of RAM reduce game speed. If we're talking in general terms, you don't ever need 32GB of RAM assigned to your game. Unless of course, you're running a heavy modpack
A 4000x4000 texture pack with 16 variants for every block type.
RAM wouldn't help at all here, as your GPU itself can only handle so large of a texture size (for example, mine supports up to 16384x16384 - this is the total size of ALL block and item textures combined as the game stitches them into a single texture atlas at runtime (draw calls can only operate on one texture at a time). Last I saw (1.13) the default atlas was 1024x512 so this means I can only run up to 256x textures, and probably less since the game (1.6.4) only reports 8192 as the maximum size that can be allocated. Interestingly, this is with 512 MB allocated (1.6.4, even heavily modded (non-Forge), only needs around 256 MB); if I allocate 1 GB it goes down to 4096, which leads to another important thing to note - you need to make sure there is enough free memory for the rest of your system (for example, the issue this person had was due to insufficient native memory, not a more traditional Java heap issue; this is more common on 32 bit but 64 bit isn't immune).